Lung cancer (LC) is the leading cause of cancer mortality with more than 1 million deaths worldwide every year. The recent National Lung Cancer Screening Trial (NLST) has proven that screening for lung cancer by low dose CT scans reduces the related mortality rate by 20%. Unfortunately, the false-positive rate was extremely high, with 96% of the 24% positive CT findings being non-cancerous. Retrospectively, individuals with false-positive findings underwent unnecessary invasive procedures that are costly and are associated with significant risks and increased mortality (N. Engl. J. Med. 2011; 365:395-409). Since low dose CT screening programs for lung cancer are expected to be launched in many countries in the near future, it is reasonable to expect a dramatic increase in the detection of small solitary pulmonary nodules (SPNs) as well as a dramatic increase in the invasive procedures, morbidity, mortality and health care costs.
Volatile Organic Compounds (VOCs) are organic molecules characterized by a high vapor pressure at ordinary, room temperature conditions. These molecules evaporate from the cell and/or from the surrounding microenvironment and enter the blood stream. Some VOCs are then secreted in exhaled breath through exchange via the lungs. VOCs that evaporate from the membrane of cancer cells induce changes in the blood chemistry. These changes are then reflected in the composition of VOCs in exhaled breath which can be used to diagnose cancer (Expert Rev. Mol. Diagn. 2011; 11: 207-217; memo 2010; 3: 106-112; J. Chromatog. B 2010; 878: 2643-2651; Lung Cancer 2010; 67: 227-231; Br. J. Cancer 2010; 103: 542-551; Nature Nanotech. 2009; 4: 669-673; BMC Cancer 2009; 9: 348; Clin. Chem. 1985; 31: 1278-1282; and Clin. Chem. Lab Med. 2009; 47: 550-560).
In recent years many attempts have been made to identify the breath VOC profile of lung cancer patients (Lancet 1999; 353: 1930-1933; Chest 2003; 123: 2115-2123; Cancer Biomark. 2007; 3: 95-109; Clinica Chimica Acta 2008; 393: 76-84; Lung Cancer 2009; 67: 227-231; Clin. Chem. 1988; 34(8): 1613-1617; Inter. J. Mass Spectro. 2007; 265: 49-59; J. Chromatography A 2009; 1216: 2749-2756; Resp. Res. 2005; 6: 71-81; and Acta Biomed. 2008; 79(1): 64-72). Several spectrometry and spectroscopy studies have shown that the (exhaled breath) VOC profile of patients with lung cancer differs from that of healthy controls without lung nodules (Expert Rev. Mol. Diagn. 2011; 11: 207-217; and memo 2010; 3: 106-112). WO 2010/079491 to one of the inventors of the present invention discloses a set of volatile organic compounds indicative of lung cancer, and methods of diagnosing or monitoring lung cancer progression using such set of volatile organic compounds.
In several cases, matrices of chemical sensors were able to differentiate between breath VOC profiles of patients with lung cancer and healthy controls (Br. J. Cancer 2010; 103: 542-551; Nature Nanotech. 2009; 4: 669-673; Nano Lett. 2008; 8: 3631-3635; Lung Cancer 2009; 64: 166-170; Thorax 2007; 62: 565-568; Amer. J. Resp. Crit. Care Med. 2005; 171: 1286-1291; Sensors, Proceedings of IEEE 2003; 2: 1333- 1337; Meas. Sci. Technol. 2005; 16: 1535-1546; and Biosensors and Bioelectronics 2003; 18: 1209-1218).
WO 2007/086986 discloses a method for detecting a target analyte/biomarker in exhaled breath comprising: a) exposing to the exhaled breath a molecular recognition agent capable of selectively binding to the target analyte/biomarker, wherein the molecular recognition agent is linked with a signaling agent; and b) detecting a signal generated by the signaling agent.
WO 2009/066293 to one of the inventors of the present invention discloses an apparatus comprising at least one chemically sensitive sensor for detecting volatile and non-volatile compounds, wherein the chemically sensitive sensor comprises cubic nanoparticle conductive cores capped with an organic coating.
WO 2010/079490 to one of the inventors of the present invention discloses a breath analyzer comprising an array of sensors of conductive nanoparticles capped with an organic coating for detecting cancer.
WO 2009/144725 to one of the inventors of the present invention discloses sensor apparatuses comprising single-walled carbon nanotubes for measuring volatile organic compounds and methods of use thereof for determining breath analytes indicative of various cancers and, in particular, lung cancer.
WO 2010/064239 to one of the inventors of the present application discloses a system comprising an array of sensors for measuring volatile organic compounds as biomarkers for diagnosis, prognosis and monitoring of renal insufficiencies.
In addition to the many studies that were aimed at identifying VOCs indicative of lung cancer from breath samples, Filipiak et al. (Cancer Cell Inter. 2008; 8: 17) disclosed a list of 60 substances observed in the headspace of medium as well as in the headspace of lung cancer cell line CALU-1. A significant increase in the concentrations of 4 VOCs and a decrease in the concentrations of 11 VOCs as compared to medium controls were detected after 18 hours. In another study, Chen et al. (Cancer 2007; 110: 835-844) identified 4 VOCs that were found to exist in all culture mediums of lung cancer cells and can be used as markers of lung cancer. Recent in vitro experiments of the headspace of cell lines identified three substances (decanal, acetophenone and 1,3-bis(1,1-dimethylethyl)-benzene) as main contributors to the separation between small cell and non-small cell lung cancer. Nine VOCs (two aldehydes, one alkane, two ketones, one alcohol and three benzene derivatives) showed differences between subtypes of non-small cell lung cancer of which 2-ethyl-l-hexanol, 1,3-dimethyl-benzene and 1,3-bis (1,1- dimethylethyl)-benzene were found at higher concentrations in the headspace of adenocarcinoma cell lines as compared to the headspace of squamous cell carcinoma cell lines (Nanomedicine (NBM) 2012; 8: 580-589).
WO 2012/023138 to the inventors of the present invention discloses methods of diagnosing, prognosing or monitoring the treatment of pre-cancerous conditions of the lung e.g. bronchial dysplasia or atypical alveolar hyperplasia (AAH), or identifying a genetic alteration which is associated with lung cancer as a means of prognosing or monitoring the treatment or the recurrence of lung cancer, or predicting a patient's response and/or resistance to various treatment regimens.
There remains an unmet need for a reliable biomarker assay technique for differentiating between benign nodules and malignant nodules in a non-invasive and cost-effective manner while dramatically reducing false-positive rates.